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Volume V. No. 3 July 1945

Register Tonnage and its Measurement, Page 226

226 REGISTER TONNAGE AND MEASUREMENT
the depth; then multiply the length by the breadth and that product by the depth
and divide the whole by 94, the quotient will give the true contents of the tonnage.
In 1773, probably influenced by the establishment about 1760 of
Lloyd's Register of Shipping, which for the first time regularly listed British
merchant vessels, and also by the chartering of dock companies that
were by law to base their charges on register tonnage, a tonnage rule was
established by Act of Parliament. It was virtually the same as the 1677
Royal Navy Rule except that the length was now to be measured along
the rabbet of the keel, from the back of the main stern-post to a perpen­dicular
from the front of the stem-post, under the bowsprit. This law was
re-enacted in 1786, 1819 and 1833 9 with slight modifications; thus in the
case of a ship afloat the length might be measured from the fore perpen­dicular
to the after end of the water-line, and 3 inches per foot draft be de­ducted
for the rake of the stern-post. This formula became known as
Builders' Old Measurement because of its continued use by shipbuilders
after it ceased to be a legal register tonnage, and the figure derived from
it is often identified as B.O.M.
The first United States tonnage law10 was passed in 1789 and continued
in effect without modification until 1864. It was based on Builders' Old
Measurement with significant differences. Length was measured 'from
the fore part of the main stem, to the after part of the stern-post, above the
upper deck,' and only three-fifths of the beam was deducted from it;
while breadth was taken 'at the broadest part above the main wales.' For
vessels with two or more decks depth was taken as one-half beam, but Con­gress
recognized the necessity for shoal-draft vessels in American waters
by specifying that in single-decked vessels the actual depth 'from the un­derside
of the deck plank to the ceiling in the hold' was to be used instead
of the half breadth. In the formula, 95 was to be used as the divisor in­stead
of 94, possibly to allow for the greater length on deck as compared
with that measured from the foot of the stern-post in the parent rule; al­though
the use of the figure 95 in North American tonnage calculations
can be traced11 as far back as 1694. The tonnage figure obtained from this
formula was often identified as C.H.·M., for 'Custom House Measure­ment.'
In the difference between the American and British rules lies the funda­mental
r eason for the differ ence between the English 'cutter model' and
the American 'sloop model' which became apparent after the first interna-
9 3 and 4 Wm. IV., c. 55, sec. 16. H. C. Folkard, The Sailing Boat (London, 1853), p. 277.
10 1 September 1789; re-enacted 2 Mar ch 1799: U. S. Stat. L., vol. I, pp. 55, 676.
11 THE AMERICAN NEPTUNE , II (1942), 338.

Articles include: 'The Fleet' by Sidney G. Morse; Voyage of the Brig Nabob from Boston to Batavia, Java, in 1833 From a letter by Captain George W. Putnam, of Salem, to his sisters Edited by Ralph Newell Thompson; The Dismal Swamp Canal by Alexander Crosby Brown; Register Tonnage and its Measurement by John Lyman; and Mutton Spankers and Ringtail Topsails by Captain P. A. McDonald. Documents, News, and Book Reviews are also included.

226 REGISTER TONNAGE AND MEASUREMENT
the depth; then multiply the length by the breadth and that product by the depth
and divide the whole by 94, the quotient will give the true contents of the tonnage.
In 1773, probably influenced by the establishment about 1760 of
Lloyd's Register of Shipping, which for the first time regularly listed British
merchant vessels, and also by the chartering of dock companies that
were by law to base their charges on register tonnage, a tonnage rule was
established by Act of Parliament. It was virtually the same as the 1677
Royal Navy Rule except that the length was now to be measured along
the rabbet of the keel, from the back of the main stern-post to a perpen­dicular
from the front of the stem-post, under the bowsprit. This law was
re-enacted in 1786, 1819 and 1833 9 with slight modifications; thus in the
case of a ship afloat the length might be measured from the fore perpen­dicular
to the after end of the water-line, and 3 inches per foot draft be de­ducted
for the rake of the stern-post. This formula became known as
Builders' Old Measurement because of its continued use by shipbuilders
after it ceased to be a legal register tonnage, and the figure derived from
it is often identified as B.O.M.
The first United States tonnage law10 was passed in 1789 and continued
in effect without modification until 1864. It was based on Builders' Old
Measurement with significant differences. Length was measured 'from
the fore part of the main stem, to the after part of the stern-post, above the
upper deck,' and only three-fifths of the beam was deducted from it;
while breadth was taken 'at the broadest part above the main wales.' For
vessels with two or more decks depth was taken as one-half beam, but Con­gress
recognized the necessity for shoal-draft vessels in American waters
by specifying that in single-decked vessels the actual depth 'from the un­derside
of the deck plank to the ceiling in the hold' was to be used instead
of the half breadth. In the formula, 95 was to be used as the divisor in­stead
of 94, possibly to allow for the greater length on deck as compared
with that measured from the foot of the stern-post in the parent rule; al­though
the use of the figure 95 in North American tonnage calculations
can be traced11 as far back as 1694. The tonnage figure obtained from this
formula was often identified as C.H.·M., for 'Custom House Measure­ment.'
In the difference between the American and British rules lies the funda­mental
r eason for the differ ence between the English 'cutter model' and
the American 'sloop model' which became apparent after the first interna-
9 3 and 4 Wm. IV., c. 55, sec. 16. H. C. Folkard, The Sailing Boat (London, 1853), p. 277.
10 1 September 1789; re-enacted 2 Mar ch 1799: U. S. Stat. L., vol. I, pp. 55, 676.
11 THE AMERICAN NEPTUNE , II (1942), 338.